lPaeesh le pemu mnxit ehess rtnisg! Oh, sorry, that was supposed to say: Please help me unmix these strings!
Somehow my strings have all become mixed up; every pair of characters has been swapped. Help me undo this so I can understand my strings again.
unmix("123456") ➞ "214365"
unmix("hTsii s aimex dpus rtni.g") ➞ "This is a mixed up string."
unmix("badce") ➞ "abcde"
The length of a string can be odd — in this case the last character is not altered (as there's nothing to swap it with).